Packaging machine and method for closing containers with lids

ABSTRACT

The invention relates to a method for closing already preformed and separated containers ( 19 ), for example trays, with a lid foil ( 24 ) in a closing station ( 3 ). The invention is characterized in that a deep-drawable foil is used as lid foil ( 24 ), that the lid foil ( 24 ) is deep-drawn in a forming means ( 23 ) of the packaging machine ( 1 ), and that the deep-drawing of the lid foil ( 24 ) is accomplished before the containers ( 19 ) are closed with the lid foil ( 24 ). The invention also relates to a packaging machine ( 1 ) suited for carrying out such a method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C.§119(a)-(d) to German patent application number DE 102009020892.5, filedMay 13, 2009, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a method for closing containers, aswell as to a packaging machine for carrying out such a method.

BACKGROUND

Packaging machines for closing already preformed and separatedcontainers are known in the form of so-called tray sealers, for examplefrom DE 10 2006 018 327 A1. Such machines are fed with already preformedand separated trays which are usually stacked and stocked after theyhave been formed. The containers are individually removed from the stockand placed onto a conveying belt where they are filled with a productfrom above. In the conventional tray sealer, a sealing foil issubsequently applied onto the trays that are open to the top whichcloses as well as seals the trays.

In conventional tray sealers, the sealing foil must not be stretched bythe product, as otherwise the sealing foil might tear off. Consequently,the trays must be comparably deep to prevent the products fromprojecting over the edge of the trays. This excessive height of thetrays, however, also involves drawbacks. On the one hand, this leads toan increase in the required amount of material and costs of a package.On the other hand, less preformed or filled trays can be accommodatedper volume, so that costs increase for the stock-keeping of the emptytrays as well as for the distribution of the filled and closed trays.

SUMMARY

It is an object of the present disclosure to overcome these drawbackswith structural means that are as simple as possible.

An embodiment of the present disclosure involves using a deep-drawablefoil for closing already preformed and separated containers, and thefoil is deep-drawn in a forming means or device of a packaging machinebefore the containers are closed with the lid foil. This deep-drawingoffers the advantage that the package can be much better adapted to therespective product than before, although the containers are alreadypreformed. In particular, products projecting over the container edgecan also be accommodated in the containers, without the lid foilstretching over the product. Moreover, there are also estheticadvantages as, in contrast to conventional tray sealers, the upper sideof each package does no longer have to be flat, but can be structured.

The lid foil may be heated upstream of and/or in the forming device topermit deep-drawing. The preheating of the lid foil upstream of theforming device can accelerate deep-drawing and reduce superfluouswaiting times of other components of the packaging machine.

It is conceivable to deep-draw the lid foil towards the side of the lidfoil facing the container during closing altogether or at least insections. In this manner, a lid section which projects into the interiorof the container is formed in the lid foil. This is in particular suitedfor products or regions of a product which are situated at a lower levelthan the edge of the container.

As an alternative or in addition, it is conceivable to deep-draw the lidfoil towards the side of the lid foil facing away from the containerduring closing altogether or at least in sections. In this manner, adome shaped lid section is formed which projects upwards over thecontainer edge and permits the accommodation of projecting productswithout the lid foil stretching over the product.

By the method according to the present disclosure, in the deep-drawingprocess, at least one concave and/or one convex section can be formed onthe side of the lid foil facing the container during closing. They canfacilitate the placement of complementary formed regions of the productsagainst the lid to prevent, for example, shifting of the products in thecontainers.

The forming device can be provided separately from the closing station.The complete packaging machine, however, becomes more compact and themethod thereby less complex, if deep-drawing is carried out within theclosing station itself.

As lid foil, a flexible foil or a hard foil could be used, if they canbe deep-drawn in a suited manner.

Depending on the product, it can be advantageous to use a multilayerfoil as lid foil. For example, a combination of an outer layerimpermeable to oxygen and an inner layer permeable to oxygen would beconceivable to permit oxygen to flow around the products.

In one variant of the invention, the lid foil or the lid section formedin it, respectively, is only placed onto the respective containers by aform fit in the form of a “slip lid”. The lid section can, for example,snap in at an edge of the container to securely connect the lid to thecontainer.

In addition or as an alternative, it is possible for the lid foil to besealed onto the containers, in particular if the interior of thecontainer is to be hermetically sealed.

If the lid foil is sealed to the containers, the transport of the closedcontainers connected with the lid foil out of the closing station cancause further lid foil to be drawn behind, which is used for closingfollowing containers. In this manner, one could do without a separateconveyor device for the lid foil.

The present disclosure also relates to a packaging machine for carryingout a method according to the present disclosure. The packaging machinecomprises a forming means or device for deep-drawing the deep-drawablelid foil.

It is appropriate for the forming device to comprise an exchangeableinsert which determines the deformation of the lid foil to a lidsection. This insert can be replaced if it is worn down, or if adifferent shape of the lids for the containers is to be produced.

Mainly in comparably thick hard foils, the pulling force acting on thelid foil only by the movement of the closed containers still connectedto the lid foil might not be sufficient. In this case, it isadvantageous to provide, in addition to a transport means for thecontainers, such as a conveyor belt or any other suitable transportdevice, a separate conveying means for the lid foil, for example a clampchain arranged on both sides which can also be used to stretch the lidfoil laterally, or any other suitable conveyor device.

The packaging machine according to the present disclosure may have atool for placing and/or sealing the lid foil onto the containers. Inthis tool, the actual closing of the containers is thus accomplished.

The tool itself can comprise a lower tool and an upper tool which can bemoved relative to each other. For example, they can open for receivingthe unclosed containers and reduce the space between them for closingand possibly evacuating and/or gassing the containers.

It is appropriate if the lower tool and the upper tool can be spacedapart by the relative movement at least far enough to correspond to thesum of the height of a container and the height of a lid section of thelid foil. In this manner, the closing tool also permits theaccommodation of containers in which the product and the lid projectover the edge of the container.

In the following, two advantageous embodiments of the present disclosureare illustrated more in detail with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a packaging machine according to thepresent disclosure;

FIGS. 2 to 8 show schematic vertical sections through a first embodimentof the packaging machine in different steps of a method according to thepresent disclosure; and

FIGS. 9 to 15 show a second embodiment of the packaging machine indifferent steps of the method according to the present disclosure.

DETAILED DESCRIPTION

In the Figures, equal and similar components are provided with the samereference numerals.

FIG. 1 shows a first embodiment of a packaging machine 1 according tothe invention in a perspective view. This embodiment is a tray sealer.The packaging machine 1 has a machine frame 2 on which a closing station3 is arranged for closing as well as possibly evacuating, gassing and/orsealing supplied, tray-shaped containers as well as for cutting a lidfoil used for closing. The closing station 3 is located under a cover 4that can be opened.

The packaging machine 1 furthermore has a feed belt 5 for feeding thecontainers, a discharge belt 6 for carrying away the closed containers,a foil feed roller 7 for taking up and feeding a roll of a lid foil, afoil stretching means 8 for stretching the lid foil, as well as a foilresidue winder 9 for winding up the foil residues that remain aftersealing. A display 10 permits the operator of the packaging machine 1 tocheck and control the operation of the packaging machine 1. To this end,operational controls 11 can be provided at the display 10, for exampleoperator panels or switches to influence the operation of the packagingmachine 1.

FIG. 2 shows, in a first embodiment of the packaging machine 1 accordingto the invention, a vertical section through the closing station 3 in aschematic view. The closing station 3 has a tool 12 which in turncomprises an upper tool 13 and a lower tool 14. The upper tool 13 andthe lower tool 14 can be moved in the vertical direction relative toeach other. The upper and lower tools 13, 14 can form a closed chamber15 between themselves in a closed state (see FIG. 3).

A lifting table 16 is provided at the lower tool 14 which can betraveled in the vertical direction via a lifting rod 17 independent ofthe lower tool 14. The lifting table 16 forms a recess or cavity 18 forreceiving a prefabricated, tray-shaped container 19. This container 19can consist, for example, of hard plastics. After preforming, aplurality of containers 19 are stacked and stocked in this manner. Theycan be individually removed from this stock and placed onto the feedbelt 5 of the packaging machine 1 to be filled there.

One can see in FIG. 2 that an edge 20 of the container rests on an edgeof the lifting table 16 or cavity 18. One can also see that thecontainer 19 is filled with a product 21 which projects upwards beyondthe level formed by the edge 20 of the container 19.

In the present embodiment, the upper tool 13 has a more complex design.It has on its part three tool components which can be traveledrelatively to each other in the vertical direction within the upper tool13 independent of each other as well as independent of the outer wall 22of the upper tool 13. The innermost tool component is a forming means 23for forming a lid section in the single- or multilayer lid foil 24advance by the foil feed roller 7. In the present embodiment, theforming means 23 may comprise any suitable forming device, such as aforming mold or tool having a concave design on a surface 25 facing thecontainer 19. The forming means 23 can have vacuum lines (not shown) tocreate a vacuum between the surface 25 and the lid foil 24.

Above the forming means 23, a sealing plate 26 is arranged which hassealing edges 27 projecting downwards. The sealing edges 27 are shapedsuch that they can contact the edge 20 of the container 19 when thesealing plate 26 is lowered.

A cutting means 28 is provided above the sealing plate 26, between thesealing plate 26 and the outer wall 22 of the upper tool 13. The cuttingmeans 28 may comprise any suitable cutting device, such as a movablecutting tool having cutting edges 29 projecting downwards which areconfigured for cutting the lid foil 24 in two. The tool 12 can moreoverhave means for evacuating and/or gassing the chamber 15 formed betweenthe upper and the lower tool 13, 14. For example, the tool 12 may beconnected to a vacuum pump, or any other suitable evacuating device,and/or a gas supply system.

The deep-drawable (e.g., thermoplastic) lid foil 24 passes over a firstdeflection roller 30 and is there deflected such that it traverses theinterior of the tool 12 essentially in parallel to the level formed bythe edge 20 of the container 19. The residual sections of the lid foil24 remaining after the containers 19 have been closed and the lidsections punched out pass over a second deflection roller 31 to aresidual foil winder 9 to be accumulated there. Between the foil feedroller 7 and the tool 12, a foil stretching means 8, which is notrepresented in FIG. 2 for a better overview, can be moreover provided.The foil stretching means 8 may be any suitable device, such as amovable plate or a system of rotatable drums or cylinders that includesone or more cylinders that are movable toward and away from anothercylinder.

Between the foil feed roller 7 and the first deflection roller 30, aheating means or a preheating means 32 (if a further heating step isperformed), respectively, is moreover provided. The heating means 32 canbe a heating plate which is heated, for example, via a thermal fluid oran electric heating medium. The heating means 32 is used to heat a givensection 33 of the lid foil 24 to a temperature which permitsthermoplastic forming of the lid foil 24 during a deep-drawingoperation.

With reference to FIGS. 2 to 8, a method according to the presentdisclosure and the operating sequence of the packaging machine 1,respectively, will now be illustrated.

FIG. 2 shows the tool 12 of the packaging machine 1 in a state in whicha tray 19 filled with a product 21 has been inserted into the cavity 18of the lifting table 16 and guided into the interior of the tool 12. Forthis purpose, the upper and the lower tools 13, 14 can be removed fromeach other to such an extent that the distance A between the lower edgeof the upper tool 13 and the upper edge of the lower tool 14 is largerthan the sum of the height of the container 19 and the projecting partof the product 21, to permit in this manner the introduction of thefilled container 19 into the tool 12. A certain section 33 of the lidfoil 24 is heated under the heating means 32.

FIG. 3 shows the tool 12 in a state in which first the lid foil 24 hasbeen conveyed far enough for the heated section 33 to be locatedunderneath the forming means 23. At this time, the feed of the lid foil24 is stopped. One can see in FIG. 3 that the upper tool 13 and thelower tool 14 move towards each other until they clamp the lid foil 24between their edges and form a closed chamber 15 between themselves. Asthe feed of the lid foil 24 is stopped, now a further section 33′ of thelid foil can be brought to the temperature required for forming under orin the heating means 32.

It could already be seen in FIG. 3 that the forming means 23 contactsthe lid foil 24 when the upper tool 13 is lowered. Arrows 34 in FIG. 4indicate that now a vacuum is created at the surface 25 of the formingmeans 23 by suited provisions. In connection with the contact betweenthe forming means 23 and the lid foil 24, this vacuum takes care thatthe heated section 33 of the lid foil 24 is pulled against the concavesurface 25 of the forming means 23 and in this manner deep-drawn to forma lid section 35.

The lid section 35 is represented in FIG. 5. It has a shape which iscomplementary to the edge 20 of the container 19 on the outer surface.On the side facing the product 21, the lid section 35 is concave.

FIG. 6 shows the tool 12 in a state in which—starting from the state inFIG. 5—the lifting table 16 was lifted until the edge 20 of thecontainer 19 came into contact with the lid foil 24. This movement ofthe lifting table 16 is indicated by arrow 36. Simultaneously—asindicated by arrow 37—the sealing plate 26 was lowered until its sealingedges 27 came into contact with the lid foil 24 from above. In thisstate, the lid foil 24 is now sealed onto the edge 20 of the container19.

Subsequently or simultaneously with the sealing, the cutting means 28 islowered—as shown in FIG. 7—, so that its cutting edges 29 cut out thelid foil 24 all around the closed container 19. This movement of thecutting means 28 is indicated by arrow 38.

In FIG. 8, the tool 12 is opened. This is done by moving the lower tool14 and the lifting table 16 downwards and the upper tool 13 with theforming means 23, the sealing plate 26 and the cutting means 28 upwards.The lid section 35 is firmly connected to the rest of the container 19by the sealing and remains at the container 19. The filled container 19can now be removed from the tool 12. At the same time, the lid foil 24can be transported forwards, while the rest of the lid foil 24 thatremains during cutting is winding up on the foil residue winder 9. Theclosing process can now be performed in the same manner for a subsequentcontainer.

FIG. 9 shows a second embodiment of a packaging machine 1 according tothe present disclosure. It differs from the first embodiment in that theforming means 23 for forming the lid sections is now no longer providedin the closing tool 12, but in the region of the heating means 32. Apartfrom that, the upper tool 13 and the lower tool 14 of the closing tool12 remain unchanged. In particular, the upper tool 13 still comprises asealing plate 26 and a cutting means 28, while the lower tool 14 stillcomprises a lifting table 16.

In the second embodiment, the forming means 23 comprises a first forminghalf 39 and a second forming half 40. As indicated by the arrows 41, thetwo forming halves 39, 40 can be moved relative to each otherperpendicular to the plane of the lid foil 24, so that they can closearound the lid foil 24 or can release the lid foil 24, respectively.

In the first forming half 39, an exchangeable inset 42 is provided. Itssurface 43 facing the lid foil 24 defines the shape of the lid section35 if the section of the lid foil 24 heated by the heating means 32 inthe opposite second forming half 40 is pulled closer by applying avacuum to the surface 43 of the inset 42 to deep-draw the lid foil 24.

FIGS. 9 to 15 show various steps of the method according to the presentdisclosure during the operation of the packaging machine 1 according tothe second embodiment. FIG. 9 shows the packaging machine 1 in a statein which a fresh section of the lid foil 24 has been brought into theforming means 23.

In FIG. 10, the two forming halves 39, 40 of the forming means 23 havebeen closed. Arrows 44 indicate that a vacuum is created at the inset 42of the forming means to place the lid foil 24 in this region against theinset 42 of the first forming half 39 and to form a lid section 35 inthis manner. The inset 42 can be exchanged if lid sections 35 having adifferent shape are to be produced.

FIG. 11 shows the state of the packaging machine 1 after the lid foil 24has been deep-drawn in the forming means 23. The lid foil 24 now has alid section 35.

In FIG. 12, the two forming halves 39, 40 have been removed from eachother. The opening 45 formed between them now must be large enough—atleast in the exiting direction out of the forming means 23—to let thedomed lid section 35 pass.

Between the state in FIG. 12 and the state in FIG. 13, the lid foil 24has been moved into the conveying direction 45 far enough for the lidsection 35 now to be positioned within the closing tool 12 over thecontainer 19 to be closed. The first deflection roller 30 here only liesagainst an outer edge of the lid foil 24, so that it does not collidewith the lid section 35 in the central region of the lid foil 24.

FIG. 14 shows the packaging machine 1 in a state in which the closingtool 12 has been closed by moving the upper tool 13 and the lower tool14 towards each other. A contact between the sealing edges 27 of thesealing plate 26 and the edge 20 of the container 19, that is close bydue to the lifting of the lifting table 16, permits to seal the lid foil24 to the container 19. Simultaneously or subsequently, the cuttingmeans 28 has been lowered to cut out the closed container. The formingmeans 23 has simultaneously closed around a new section of the lid foil24 to form a further lid section 35.

In FIG. 15, the forming means 23 as well as the closing tool 12 havebeen opened. The closed container 19 can now be removed from the tool12, and the cycle can start anew.

Starting from the two embodiments described in detail, a methodaccording to the present disclosure and a packaging machine according tothe present disclosure can be modified in many ways. It is, for example,conceivable for the lid sections 35 not to be sealed to the edge 20 ofthe container 19, but to only be placed onto the container 19 by a formfit in the form of slip lids. It is moreover possible to impart anyarbitrary shape to the lid section 35. In the first embodiment, too, theforming means 23 can have an exchangeable inset 42. Though it is notshown, several lid sections 35 can be manufactured one after or one nextto the other in the forming means 23, and several containers 19 can besimultaneously closed in the closing station 3.

While exemplary embodiments of the invention have been illustrated anddescribed, it is not intended that these embodiments illustrate anddescribe all possible forms of the invention. Rather, the words used inthe specification are words of description rather than limitation, andit is understood that various changes may be made without departing fromthe spirit and scope of the invention. Additionally, the features ofvarious implementing embodiments may be combined to form furtherembodiments of the invention.

1. A method for closing already preformed and separated containers witha lid foil in a closing station of a packaging machine, the methodcomprising: deep-drawing the lid foil with a forming device of thepackaging machine; and closing the containers with the lid foil in theclosing station; wherein for each container, the deep-drawing isperformed prior to the closing.
 2. The method according to claim 1further comprising heating the lid foil upstream of the forming deviceand/or in the forming device.
 3. The method according to claim 1 whereinthe deep-drawing is performed such that the lid foil is deep-drawn atleast in sections towards a side of the lid foil facing the containersduring the closing.
 4. The method according to claim 1 wherein thedeep-drawing is performed such that the lid foil is deep-drawn at leastin sections towards a side of the lid foil facing away from thecontainers during the closing.
 5. The method according to claim 1wherein for each container the deep-drawing is performed such that atleast one concave and/or one convex section is formed on a side of thelid foil facing the container during the closing.
 6. The methodaccording to claim 1 wherein the deep-drawing is carried out in theclosing station.
 7. The method according to claim 1 wherein the lid foilcomprises a flexible foil or a hard foil.
 8. The method according toclaim 1 wherein the lid foil comprises a multilayer foil.
 9. The methodaccording to claim 1 wherein for each container the closing comprisesplacing the lid foil onto the container by a form fit.
 10. The methodaccording to claim 1 wherein for each container the closing comprisessealing the lid foil onto the container.
 11. The method according toclaim 10 wherein, after sealing the lid foil onto the containers, thelid foil is moved along by movement of the closed containers.
 12. Apackaging machine for closing already preformed and separated containerswith a lid foil, the packaging machine comprising: a forming deviceconfigured to deep draw the lid foil to form lid sections; and a closingstation for closing the containers with the lid sections; wherein thepackaging machine is operated such that, for each container, a lidsection is formed prior to closing the container with the lid section.13. The packaging machine according to claim 12 wherein, for eachcontainer, the forming device is configured to form at least one concaveand/or one convex section on a side of the lid foil facing the containerduring the closing of the container at the closing station.
 14. Thepackaging machine according to claim 12 wherein the forming devicecomprises an exchangeable insert for deforming the lid foil.
 15. Thepackaging machine according to claim 12 further comprising a conveyordevice for conveying the lid foil, and a transport device fortransporting the containers.
 16. The packaging machine according toclaim 15 wherein the conveyor device comprises a clamp chain.
 17. Thepackaging machine according to claim 12 wherein the closing stationcomprises a tool for placing and/or sealing the lid foil onto thecontainers.
 18. The packaging machine according to claim 17 wherein thetool comprises a lower tool and an upper tool, wherein at least one ofthe lower tool and the upper tool is movable with respect to the otherof the lower tool and the upper tool.
 19. The packaging machineaccording to claim 18 wherein the lower tool and the upper tool areconfigured to be spaced apart by the relative movement at least farenough to correspond to the sum of a height of a container and a heightof a lid section of the lid foil.
 20. The packaging machine according toclaim 12 wherein the forming device is located at the closing station.